Patients who develop sepsis and multiple organ failure after surgery or trauma face significant morbidity and mortality. Our approach since originally synthesizing the macrophage-deactivating, low molecular weight, multivalent guanylhydrazone CN1-1493, has been to use this compound as a tool to probe physiological echanisms that inhibit systemic inflammatory mediator responses. Studies of CNI-1493 mechanism of action in animal models of endotoxemia and sepsis unexpectedly revealed a neural mechanism to inhibit systemic inflammation through vagus nerve stimulation. These surprising observations revealed a previously unrecognized neuroimmune mechanism now termed the "cholinergic anti-inflammatory pathway," which rapidly deactivates macrophages. This opened a new avenue for investigating regulation of systemic inflammation that we have pursued. Preliminary Results show that electrical stimulation of the vagus nerve specifically inhibits macrophage activation, prevents TNF synthesis in liver and heart, and significantly attenuates the systemic inflammatory response to endotoxemia. Vagus nerve stimulators are widely used in the treatment of epilepsy (they are quite safe) but their impact on immune responses was previously unknown. This application now seeks funding to pursue this line of basic physiological investigation, and to define the impact of the cholinergic anti-inflammatory pathway on regulation of systemic and organ-specific macrophage activation in vivo in standard animal models of endotoxemia and sepsis. Specific Aim 1 will establish the physiological basis for the anti-inflammatory action of vagus nerve regulation of macrophage activation in specific organs by stimulating and selectively denervating the vagus nerve input to major macrophage-containing organs in the context of 1) endotoxemia and 2) sepsis. Specific Aim 2 will assess the influence of vagus nerve stimulation on early and late systemic inflammatory cytokine responses in a clinically relevant model of hemorrhagic shock followed by sepsis. The proposed approach will address whether therapeutic, cytokine-suppressing utilization of vagus nerve stimulators can reduce mortality; or indeed cause the opposite effect by increasing susceptibility to septic complications in the traumatized, shocked host. The mechanistic insights derived from understanding how vagus nerve stimulation deactivates macrophages, and whether this strategy can be used in the milieu of endotoxemia or post-traumatic sepsis, are critical for the design of future therapies targeting the pathobiology of sepsis.